IL‐6, IFN‐γ and TNF‐α production by liver‐associated T cells and acute liver injury in rats administered concanavalin A

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Abstract
The relationship between the development of acute hepatitis and the production of TNF-α IFN-γ and IL-6 by liver-associated T lymphocytes following intravenous injection of concanavalin A (Con A) was studied in rats. Following a single injection of Con A, there was a dose and time-dependent correlation in the serum levels of serum alanine aminotransferase (ALT), IL-6, IFN-γ and TNF-α. These increases correlated with an increase in the numbers of CD4+, CD8+ and CD25+ T cells in blood and CD4+ and CD25+ T cells in the liver perfusate, but not with CD8+ T cells in liver perfusate. Increased levels of IL-6, IFN-γ and TNF-α were constitutively produced by liver-associated CD4+ T cells when cultured. In Con A-stimulated cultures, liver-associated CD4+ T cells secreted increasing levels of TNF-α in a time-dependent manner following Con A injection, but TNF-α production by peripheral blood lymphocytes was transient with peak levels detected at 1 h which then declined over 24 h. Histological examination of the liver revealed fatty change, hepatocyte degeneration and necrosis, with an associated cell infiltrate of neutrophils and CD4+ T cells both in the portal areas and around the central veins. These results support the hypothesis that Con A-induced liver damage is mediated by CD4+ T cells acting within the liver, at least in part through the secretion of TNF-α, IFN-γ and IL-6.